The present technology relates to an analog-to-digital (AD) conversion apparatus and a signal processing system that are configured to be applied to a receiver in radio communication, and furthermore an audio device, a medical measuring device, and the like.
FIG. 1 is a diagram showing an outline structure of an AD converter (ADC; Analog-to-Digital Converter).
In FIG. 1, X represents an input voltage of an AD converter 1, and the input voltage X is an analog signal. Meanwhile, Y represents an output voltage of the AD converter 1, and the output voltage Y is a digital signal.
The AD converter 1 generates a distortion caused by non-ideal characteristics of circuit elements used inside. When a circuit has a distortion, the output includes not only fundamental wave components of a signal but also harmonic components.
In the harmonic components, even-order components may have a sufficient attenuation amount with an AD converter having an all-differential structure, but odd-order components appear in the output as they are.
When the AD converter 1 shown in FIG. 1 has distortion characteristics, the output Y with respect to the comparatively small input X is expressed as the following formula 1.Y=aiX+a3X3+a5X5+ . . .  (Formula 1)
In the formula, ai represents a gain of ith-order distortion components, and an even-order distortion is not assumed to be generated as mentioned above.